1. Field of the Invention
The present invention relates to a local-dimming method, a light source apparatus performing the local-dimming method and a display apparatus having the light source apparatus. More particularly, the present invention relates to a local-dimming method of driving light-emitting blocks which incorporates color dimming, a light source apparatus performing the local-dimming method and a display apparatus having the light source apparatus.
2. Description of the Related Art
Liquid crystal display (LCDs) devices are used in a wide range of portable and stationary applications including laptop computers, small-size and large-size television sets, and other applications, because the LCDs have low power consumption and are thin and light-weight. An LCD device includes an LCD panel displaying an image by controlling light transmissivity of liquid crystal and also includes a backlight assembly disposed behind the LCD panel and providing light to the LCD panel.
The LCD panel includes an array substrate having a plurality of thin-film transistors (TFTs) arranged in a matrix. Another substrate (e.g. a color filter substrate in a color LCD) faces the array substrate. A liquid crystal layer is disposed between the array substrate and the color filter substrate. The backlight assembly includes a light source such as a cold cathode fluorescent lamp (CCFL). Recently light-emitting diodes (LED) having been used as light sources due to their low power consumption and high color reproducibility.
In order to reduce power consumption and increase the contrast ratio, modern LCD devices use local dimming technology which controls the light energy emitted by the backlight assembly based on the image being displayed. In dimming technology, if the image is dark, then the light source is dimmed but the liquid crystal is made more transmissive to compensate for the dimming and obtain the desired luminance. The dimming can be based on the highest brightness present in the image. In an LCD using the local dimming technology, the LCD panel is divided into blocks, and each block is dimmed separately based on the image portion corresponding to the block (e.g. based on the highest luminance of the block's image portion). Some such LCDs use one-dimensional dimming technology if the backlight assembly includes a linear-shaped light source such as a linear lamp, or use two-dimensional dimming technology if the backlight assembly has an array of point light sources such as LEDs.
Some LCD devices combine red, green and blue LEDs to generate white light for the LCD panel. In such devices, further reduction of the power consumption can be obtained using a three-dimensional dimming technology (referred to as “color-dimming”) which provides separate luminance control over the LEDs of each color depending on the image being displayed. For example, the image may allow a block's red LEDs to be dimmed more than the green or blue LEDs, and correspondingly the liquid crystal is made more transmissive for the red LEDs than for the green or blue LEDs. Improved techniques for color dimming are desired.